A multi-stage torque control method applied to the tail coiling of hot-rolled strip steel

Abstract

This invention discloses a multi-stage torque control method for the tail coiling of hot-rolled strip steel. The method comprises four steps: optimizing the initial set speed during coiling torque control through thickness layering; the torque control stage after coiling biting; the torque control speed maintenance stage after finishing rolling and steel ejection; and calculating the end point of the multi-stage torque control. Combining the superimposed lead amount in the torque control of existing hot-rolled coiling procedures, multi-stage parameter control is adopted for the relevant control modes. The switching point is based on conventional rules output by the software, using the mill's steel ejection point for switching. After selecting the switching point, multi-stage parameter control is employed to maintain the strip tension during coiling while limiting speed increases. This multi-stage torque control method for the tail coiling of hot-rolled strip steel effectively reduces the occurrence of loose coiling at the tail of the coil after finishing rolling and improves the coiling quality at the tail.

Description

Technical Field

[0001] This invention relates to the field of metal metallurgical manufacturing, and in particular to a multi-stage torque control method for the tail winding of hot-rolled strip steel with automatic control in metallurgical steel rolling. Background Technology

[0002] Currently, a two-stage torque control technology for the tail of hot-rolled strip is frequently used on the hot rolling production lines of various steel production enterprises. This technology can prevent abnormal increases in the coiling speed caused by loss of tension at the tail of the coil during the production process, thus avoiding quality problems at the tail of the strip.

[0003] For the transmission control of the key component of the above technology - the hot-rolled coiling drum - there are generally two types of closed-loop control: speed loop and current loop, which are responsible for their respective target control. Among them, torque control is used for the coiling at the tail end of the coiler until the side guide plate. The current speed is maintained and then switched to speed control. In order to maintain a smooth transition of the tail winding torque, the pinch rolls need to have sufficient pressure settings and matching tail winding tension settings to ensure that the tail winding tension smoothly switches from the drum to the final stand of the finishing mill between the drum and the pinch rolls. However, the actual state of the pinch rolls is the most difficult to control. Various factors can easily cause instability in control, resulting in the tail end losing tension after the tail finishing mill throws the steel, leading to the loosening of the coil at the tail end.

[0004] After extensive work and summarization by on-site operators, the following problems were identified with the existing technology:

[0005] After the strip leaves the finishing mill, due to insufficient pressure from the pinch rolls, the friction generated between the strip and the drum is insufficient to support the winding torque. As a result, the strip slips between the rolls, causing the original saturated current of the drum to drop. Since the target speed is much higher than the current speed, the current regulator will continue to increase the current to speed up the roll. However, due to the pressure of the pinch rolls, the current will never reach the saturation value of the torque setting. At this point, the drum speed will continue to increase to the torque control stage (1+k) - usually about 1.2 times the speed setting. This is the abnormal phenomenon of drum speed increase seen on site.

[0006] Since the tail of the strip needs to be decelerated to a preset fixed speed for entering the coiler on the roller table, the deceleration point L1 will be calculated based on the current strip speed and the target speed of entering the coiler at the moment of the strip being ejected from the finishing mill, and the deceleration efficiency is set to calculate the distance (in meters) from the tail of the strip to the coiler when deceleration starts. However, due to abnormal speed increase, the actual strip speed will be much higher than the theoretical speed at the calculated moment. This not only affects the coiling stability during the deceleration stage, but also the actual speed of entering the coiler will be higher than the theoretically controlled set speed. Coupled with the abnormal coiler speed increase mentioned above, it will cause instability in the entire tail coiling process, thus resulting in tail quality problems.

[0007] Patent number CN201810398010.3 - A method for controlling the deceleration distance of the tail of a hot-rolled coiled strip. The method of this invention includes: obtaining the first speed of the strip being ejected from the finishing mill; obtaining the second speed of the coiler; obtaining the deceleration rate of the strip based on the first speed and the second speed; obtaining the deceleration distance of the strip based on the deceleration rate, the first speed and the second speed; obtaining the deceleration point of the strip based on the deceleration distance; obtaining the deceleration time of the strip based on the first speed and the deceleration point; when the strip being ejected from the finishing mill reaches the deceleration time, the strip starts to decelerate. By the above method, the technical problem of the coiling flying phenomenon caused by inaccurate setting of the deceleration distance of the coiler in the prior art is solved.

[0008] However, this invention controls the deceleration time point of the coiling speed by calculating the time when the tail of the strip reaches the coiler after the strip is ejected, rather than avoiding the abnormal speed increase after the coiling ejection through multi-segment control of the tail torque.

[0009] Patent number CN201610024098.3 - A variable pressure control method for pinch rolls in the coiling of heavy-gauge carbon steel in hot tandem rolling. Applicable to carbon steel with a thickness of ≥8 mm. Its feature is that the original pressure coefficient is applied when the coiled strip is at the head and body parts; when the tail of the coiled strip is ejected from the last finishing mill stand, the variable pressure coefficient is applied; the variable pressure coefficient K = K1 + △K, where K: variable pressure coefficient (0 < K < 1), K1: original pressure coefficient (generally taking a value of 0.4); △K: additional pressure coefficient, with a value range of 0.0 - 0.3. This application solves the problem of scratches caused by the upward bowing of the tail of heavy-gauge carbon steel.

[0010] However, the invention solves some problems of the surface qualification rate of hot-rolled products by changing the pinch roll pressure control, but does not solve the problem of abnormal speed increase during the coiling of the tail of the strip due to insufficient pinch roll pressure resulting in tail coiling quality problems. Summary of the Invention

[0011] In summary, existing technologies struggle to address the issue of insufficient pinch roll pressure causing strip tail-end slack and resulting abnormal coiling speed, leading to poor coiling quality. This invention proposes a multi-segment torque control method for hot-rolled strip tail-end coiling. This method combines the superimposed lead amount in existing hot-rolling coiling torque control procedures with multi-segment parameter control for the relevant control modes. Switching points are based on conventional rules output by the software, using the mill's steel-throwing point for switching. After selecting the switching point, multi-segment parameter control is employed, effectively mitigating the loosening phenomenon at the coil tail after strip tail finishing and improving coiling quality.

[0012] The present invention provides a multi-stage torque control method for the tail winding of hot-rolled strip steel, the specific steps of which are as follows:

[0013] 1. A multi-stage torque control method applied to the tail coiling of hot-rolled strip steel, the specific steps of which are as follows:

[0014] 1) Optimize the initial set speed for winding torque control by using thickness layering:

[0015] V ref =K θ K S K T K ld ×V syn

[0016] In the formula:

[0017] V ref : Given drum speed, unit: meters per second;

[0018] K θ : Strip thickness coefficient;

[0019] K S : Strip lateral compression coefficient;

[0020] K T : Temperature coefficient of strip steel;

[0021] K ld : Belt coefficient;

[0022] V syn : Finishing mill synchronous speed, unit: meters per second;

[0023] The above K θ K S K T The coefficients were determined by field tests, where K... θ The strip thickness coefficient, determined experimentally, should be as small as possible when the strip thickness is relatively thin. Considering the given speed and the strip running speed, its lower limit is determined to be 98.2%, or 0.982. K...S The determination of the strip side pressure coefficient is based on the influence of side pressure on the strip edge, while K T The temperature coefficient of strip steel is inversely proportional to temperature; the higher the temperature, the smaller the correction factor.

[0024] The principle behind this design is that the existing technology for controlling the speed at the tail of the drum is as follows:

[0025] V ref =V syn ×K ld

[0026] V ref Given drum speed

[0027] V syn Finishing mill synchronous speed (F7 speed)

[0028] K ld : Belt coefficient

[0029] The existing technology for speed control at the tail end of the winding process is relatively rigid, and the closed-loop self-control adjustment factors are limited, which can easily lead to insufficient speed setting and thus cause abnormal roll shape at the tail end of the finished roll. After introducing thickness stratification, the present invention makes it easier to match the speed setting according to the different shapes and specifications of the actual slab.

[0030] 2) Torque control stage after coiling and biting:

[0031] When the automated control system L1 receives the actual torque feedback from the drive, if the torque setting is reached, it will automatically generate a tension-building signal. At this time, the drum speed setpoint will switch to the speed setpoint of the torque control mode, specifically:

[0032] The speed is increased by α based on the current strip speed, and this increased speed is used as the speed lead setpoint for the drum drive control system. Since the strip is still being rolled by the stand, this change in the speed target setting will not affect the actual control because the current regulator is still in forced saturation of the torque setpoint. At this time, the system switches to:

[0033] V ref =K θ K S K T K ld ×(V syn +V syn ×α)

[0034] In the formula:

[0035] V ref : Given drum speed, unit: meters per second;

[0036] Kθ : Strip thickness coefficient;

[0037] K S : Strip lateral compression coefficient;

[0038] K T : Temperature coefficient of strip steel;

[0039] K ld : Belt coefficient;

[0040] V syn : Finishing mill synchronous speed, unit: meters per second;

[0041] α: velocity of superposition;

[0042] The principle behind this design is that after the coiler head bites in and the strip is wound onto the drum, the drum speed will drop to the strip speed due to the clamping speed of the finishing mill stand. At this time, because speed control is still in place, the drum drive will increase the current to accelerate to the advanced set speed. However, due to the torque setting, once the current regulator output current reaches the torque limit setting, the drum will maintain the speed at which the current regulator is saturated. In other words, the adjustment capability of the current regulator is forcibly limited by the torque setting value of the automatic control system L1, which is what we call the torque control stage in process control.

[0043] 3) Torque control and speed maintenance stage after finishing rolling:

[0044] 3.1) Switching points for multi-segment speed control:

[0045] After the torque control stage following the coiling and biting of the steel in step 2), the multi-segment speed control switching point of this stage is entered to ensure the tension before the steel is thrown out in the finishing mill. In this step, among the 7 stands F1 to F7 of the finishing mill, stand F6 is selected for switching. The speed before coiling is maintained until the signal ends. By using RS trigger programming, the superposition speed of α is still used as a parameter when coiling and tension building up to the switching point. After the switching point, the original torque control mode can be maintained, and even if the tension is lost and the speed is increased, the speed will not be too high.

[0046] 3.2) Setting of multi-segment speed superposition:

[0047] In this step, an additional control is added to the coiling torque control, i.e., the additional speed α = 0.2. This additional control method ensures that the strip tension is maintained until the end of the strip reaches the side guide plate. Multi-segment parameters are used according to the actual control. The switching point is based on the conventional rules output by the software, and the switching is performed at the steel throwing point of the finishing mill F6 stand. The speed is maintained before coiling. RS trigger programming is used. The additional control method is still used from coiling tension establishment to the switching point. After the switching point, the finishing mill synchronous speed is increased by 2% to 8% for speed control. This maintains the original torque control mode and prevents excessive speed increase even if tension is lost.

[0048] The principle behind this design is that, through the control program for setting the drum speed, the key point lies in the torque control stage. The drum speed value is set based on the strip speed plus a superimposed speed of α = 0.2 as the speed lead. After the strip is thrown, the drum loses tension current, and neither the speed nor the torque control loop is saturated. Therefore, the speed regulator will quickly adjust towards this lead target value, resulting in a speed increase. If we change the speed lead of 0.2 in the torque control to 0 at the second stage switching point, the drum speed will be set and controlled according to the actual theoretical speed of the strip. Even if the winding torque does not reach the set value, it at least ensures a smooth transition control at the speed at the moment of strip throwing.

[0049] 4) Calculation of the end point of multi-stage torque control:

[0050] This step uses the strip tail tracking data as the end point of the multi-segment control, specifically as follows:

[0051] The tail tracking start point is based on the strip ejection signal from the last stand of the finishing mill. Tail tracking data recording begins when the ejection signal is generated. The tracking data is recorded using a scan cycle accumulation method, specifically the following formula:

[0052]

[0053] s t1 The speed measurement value of the roller conveyor detected by the pinch roll encoder in the first scan cycle;

[0054] s t2 : The speed measurement value of the roller conveyor detected by the pinch roller encoder in the second scanning cycle;

[0055] s t3 : The speed measurement value of the roller conveyor detected in the third scan cycle of the pinch roller encoder;

[0056] s tn: The speed measurement value of the roller conveyor detected by the pinch roll encoder in the nth scan cycle;

[0057] S tn The cumulative value across all scan cycles, i.e., the tail tracking value;

[0058] Since the physical distance from the rolling center point of the last stand of the finishing mill to the guide plate at the entrance of the coiler is fixed, this physical distance is S. x When the formula judges: S tn ≥S x When the strip tail is about to lose tension control from the pinch rolls and the winding speed needs to be reduced, torque control ends and speed control switches to the winding tail.

[0059] According to a multi-stage torque control method for hot-rolled strip coiling at the tail end of the present invention, in step 1), the strip thickness coefficient K... θ The range of values ​​for is as follows:

[0060] When the strip thickness is less than or equal to 2.1 mm, K θ =0.982; When the strip thickness is less than or equal to 3.5 mm and greater than 2.1 mm, K θ =0.996; When the strip thickness is less than or equal to 7.5mm and greater than 3.5mm, K θ =1.052;

[0061] According to a multi-stage torque control method for hot-rolled strip coiling at the tail end of the present invention, in step 1), the strip side pressure coefficient K... S The range of values ​​for is as follows:

[0062] When the lateral pressure is less than or equal to 70 mm, K S =0.975; when the lateral pressure is less than or equal to 110 mm and greater than 70 mm, K S =0.991; When the lateral pressure is greater than 110mm, K S =1.034;

[0063] According to a multi-stage torque control method for hot-rolled strip coiling at the tail end of the present invention, in step 1), the strip temperature coefficient K... T The range of values ​​for is as follows:

[0064] When the temperature is less than or equal to 750℃, K T =1.055; K is calculated when the temperature is less than or equal to 950℃ and greater than 750mm℃. T =0.986; when the temperature is greater than 950℃, K T =0.964;

[0065] According to a multi-segment torque control method for hot-rolled strip winding at the tail end of the present invention, in step 2), the value range of the superposition speed α is 0.2 to 0.8.

[0066] The multi-stage torque control method for the tail winding of hot-rolled strip steel according to the present invention has achieved the following beneficial effects:

[0067] 1) The present invention provides a multi-segment torque control method for hot-rolled strip coiling at the tail end. Combining the superimposed advance amount in the torque control of the existing hot-rolled coiling program, the method adopts multi-segment parameter control for the relevant control mode. The switching point is based on the conventional rules output by the software and is switched using the mill throwing point. After selecting the switching point, multi-segment parameter control is adopted to maintain the tension of the strip during coiling while limiting the increase in speed.

[0068] 2) The multi-stage torque control method of the present invention applied to the tail winding of hot-rolled strip steel can effectively improve the occurrence of loose coiling at the tail of the steel coil after the strip tail finishing rolling and improve the winding quality of the tail of the steel coil. Attached Figure Description

[0069] Figure 1 This is a flowchart illustrating the implementation of a multi-stage torque control method for the tail winding of hot-rolled strip steel according to the present invention.

[0070] Figure 2 This is a simplified diagram of the rolling mill layout for a hot rolling production line. Detailed Implementation

[0071] The following description, in conjunction with the accompanying drawings and embodiments, further describes the technical means, creative features, objectives, and effects of the multi-stage torque control method for the tail winding of hot-rolled strip steel according to the present invention.

[0072] Example

[0073] like Figure 1 and Figure 2 As shown, the multi-stage torque control method of the present invention applied to the tail winding of hot-rolled strip steel includes the following specific steps:

[0074] 1) Optimize the initial set speed for winding torque control by using thickness layering:

[0075] V ref =K θ K S K T K ld ×V syn

[0076] In the formula:

[0077] V ref: Given drum speed, unit: meters per second;

[0078] K θ : Strip thickness coefficient;

[0079] K S : Strip lateral compression coefficient;

[0080] K T : Temperature coefficient of strip steel;

[0081] K ld : Belt coefficient;

[0082] V syn : Finishing mill synchronous speed, unit: meters per second;

[0083] The above K θ K S K T The coefficients were determined by field tests, where K... θ The strip thickness coefficient, determined experimentally, should be as small as possible when the strip thickness is relatively thin. Considering the given speed and the strip running speed, its lower limit is determined to be 98.2%, or 0.982. K... S The determination of the strip side pressure coefficient is based on the influence of side pressure on the strip edge, while K T The temperature coefficient of strip steel is inversely proportional to temperature; the higher the temperature, the smaller the correction factor.

[0084] 2) Torque control stage after coiling and biting:

[0085] When the automated control system L1 receives the actual torque feedback from the drive, if the torque setting is reached, it will automatically generate a tension-building signal. At this time, the drum speed setpoint will switch to the speed setpoint of the torque control mode, specifically:

[0086] The speed is increased by α based on the current strip speed, and this increased speed is used as the speed lead setpoint for the drum drive control system. Since the strip is still being rolled by the stand, this change in the speed target setting will not affect the actual control because the current regulator is still in forced saturation of the torque setpoint. At this time, the system switches to:

[0087] V ref =K θ K S K T K ld ×(V syn +V syn ×α)

[0088] In the formula:

[0089] V ref : Given drum speed, unit: meters per second;

[0090] K θ : Strip thickness coefficient;

[0091] K S : Strip lateral compression coefficient;

[0092] K T : Temperature coefficient of strip steel;

[0093] K ld : Belt coefficient;

[0094] V syn : Finishing mill synchronous speed, unit: meters per second;

[0095] α: velocity of superposition;

[0096] 3) Torque control and speed maintenance stage after finishing rolling:

[0097] 3.1) Switching points for multi-segment speed control:

[0098] After the torque control stage following the coiling and biting of the steel in step 2), the multi-segment speed control switching point of this stage is entered to ensure the tension before the steel is thrown out in the finishing mill. In this step, among the 7 stands F1 to F7 of the finishing mill, stand F6 is selected for switching. The speed before coiling is maintained until the signal ends. By using RS trigger programming, the superposition speed of α is still used as a parameter when coiling and tension building up to the switching point. After the switching point, the original torque control mode can be maintained, and even if the tension is lost and the speed is increased, the speed will not be too high.

[0099] 3.2) Setting of multi-segment speed superposition:

[0100] In this step, an additional control is added to the coiling torque control, i.e., the additional speed α = 0.2. This additional control method ensures that the strip tension is maintained until the end of the strip reaches the side guide plate. Multi-segment parameters are used according to the actual control. The switching point is based on the conventional rules output by the software, and the switching is performed at the steel throwing point of the finishing mill F6 stand. The speed is maintained before coiling. RS trigger programming is used. The additional control method is still used from coiling tension establishment to the switching point. After the switching point, the finishing mill synchronous speed is increased by 2% to 8% for speed control. This maintains the original torque control mode and prevents excessive speed increase even if tension is lost.

[0101] 4) Calculation of the end point of multi-stage torque control:

[0102] This step uses the strip tail tracking data as the end point of the multi-segment control, specifically as follows:

[0103] The tail tracking start point is based on the strip ejection signal from the last stand of the finishing mill. Tail tracking data recording begins when the ejection signal is generated. The tracking data is recorded using a scan cycle accumulation method, specifically the following formula:

[0104]

[0105] s t1 The speed measurement value of the roller conveyor detected by the pinch roll encoder in the first scan cycle;

[0106] s t2 : The speed measurement value of the roller conveyor detected by the pinch roller encoder in the second scanning cycle;

[0107] s t3 : The speed measurement value of the roller conveyor detected in the third scan cycle of the pinch roller encoder;

[0108] s tn : The speed measurement value of the roller conveyor detected by the pinch roll encoder in the nth scan cycle;

[0109] S tn The cumulative value across all scan cycles, i.e., the tail tracking value;

[0110] Since the physical distance from the rolling center point of the last stand of the finishing mill to the guide plate at the entrance of the coiler is fixed, this physical distance is S. x When the formula judges: S tn ≥S x When the strip tail is about to lose tension control from the pinch rolls and the winding speed needs to be reduced, torque control ends and speed control switches to the winding tail.

[0111] In step 1), the strip thickness coefficient K θ The range of values ​​for is as follows:

[0112] When the strip thickness is less than or equal to 2.1 mm, K θ =0.982; When the strip thickness is less than or equal to 3.5 mm and greater than 2.1 mm, K θ =0.996; When the strip thickness is less than or equal to 7.5mm and greater than 3.5mm, K θ =1.052.

[0113] In step 1), the strip side compression coefficient K S The range of values ​​for is as follows:

[0114] When the lateral pressure is less than or equal to 70 mm, K S =0.975; when the lateral pressure is less than or equal to 110 mm and greater than 70 mm, K S=0.991; When the lateral pressure is greater than 110mm, K S =1.034.

[0115] In step 1), the strip temperature coefficient K T The range of values ​​for is as follows:

[0116] When the temperature is less than or equal to 750℃, K T =1.055; K is calculated when the temperature is less than or equal to 950℃ and greater than 750mm℃. T =0.986; when the temperature is greater than 950℃, K T =0.964.

[0117] In step 2), the value of the superposition velocity α ranges from 0.2 to 0.8.

[0118] This invention discloses a multi-segment torque control method for the tail coiling of hot-rolled strip steel. It combines the superimposed lead amount in the torque control of existing hot-rolling coiling procedures with multi-segment parameter control for the relevant control modes. The switching point is based on conventional rules output by the software, using the mill's steel-throwing point for switching. After selecting the switching point, multi-segment parameter control maintains the strip tension during coiling while limiting speed increases. This invention effectively reduces the occurrence of loose coiling at the tail of the strip after finishing rolling, thus improving the coiling quality at the tail of the strip.

[0119] However, those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any changes or modifications to the above embodiments within the spirit and essence of this application will fall within the scope of the claims of this application.

Claims

1. A multi-stage torque control method applied to the tail coiling of hot-rolled strip steel, the specific steps of which are as follows: 1) Optimize the initial set speed for winding torque control by using thickness layering: In ref =K θ K S K T K ld ×V syn In the formula: V ref : Given drum speed, unit: meters per second; K θ : Strip thickness coefficient; K S : Strip lateral compression coefficient; K T : Temperature coefficient of strip steel; K ld : Belt coefficient; V syn : Finishing rolling synchronous speed, unit: meters per second; The above K θ K S K T The coefficients were determined by field tests, where K... θ The strip thickness coefficient, determined experimentally, should be as small as possible when the strip thickness is relatively thin. Considering the given speed and the strip running speed, its lower limit is determined to be 98.2%, or 0.

982. K... S The determination of the strip side pressure coefficient is based on the influence of side pressure on the strip edge, while K T The temperature coefficient of strip steel is inversely proportional to temperature; the higher the temperature, the smaller the correction factor. 2) Torque control stage after coiling and biting: When the automated control system L1 receives the actual torque feedback from the drive, if the torque setting is reached, it will automatically generate a tension-building signal. At this time, the drum speed setpoint will switch to the speed setpoint of the torque control mode, specifically: The speed is increased by α based on the current strip speed, and this increased speed is used as the speed lead setpoint for the drum drive control system. Since the strip is still being rolled by the stand, this change in the speed target setting will not affect the actual control because the current regulator is still in forced saturation of the torque setpoint. At this time, the system switches to: V ref =K θ K S K T K ld ×(V syn +V syn ×α) In the formula: V ref : Given drum speed, unit: meters per second; K θ : Strip thickness coefficient; K S : Strip lateral compression coefficient; K T : Temperature coefficient of strip steel; K ld : Belt coefficient; V syn : Finishing rolling synchronous speed, unit: meters per second; α: velocity of superposition; 3) Torque control and speed maintenance stage after finishing rolling: 3.1) Switching points for multi-segment speed control: After the torque control stage following the coiling and biting of the steel in step 2), the multi-segment speed control switching point of this stage is entered to ensure the tension before the steel is thrown out in the finishing mill. In this step, among the 7 stands F1 to F7 of the finishing mill, stand F6 is selected for switching. The speed before coiling is maintained until the signal ends. By using RS trigger programming, the superposition speed of α is still used as a parameter when coiling and tension building up to the switching point. After the switching point, the original torque control mode can be maintained, and even if the tension is lost and the speed is increased, the speed will not be too high. 3.2) Setting of multi-segment speed superposition: In this step, an additional control is added to the coiling torque control, i.e., the additional speed α = 0.

2. This additional control method ensures that the strip tension is maintained until the end of the strip reaches the side guide plate. Multi-segment parameters are used according to the actual control. The switching point is based on the conventional rules output by the software. The switching point is at the steel throwing point of the finishing mill F6 stand. The speed is maintained before coiling. RS trigger programming is used. The additional control method is still used from coiling tension building to the switching point. After the switching point, the finishing mill synchronous speed is increased by 2% to 8% for speed control. This can maintain the original torque control mode and prevent excessive speed increase even if tension is lost. 4) Calculation of the end point of multi-stage torque control: This step uses the strip tail tracking data as the end point of the multi-segment control, specifically as follows: The tail tracking start point is based on the strip ejection signal from the last stand of the finishing mill. Tail tracking data recording begins when the ejection signal is generated. The tracking data is recorded using a scan cycle accumulation method, specifically the following formula: s t1 The speed measurement value of the roller conveyor detected by the pinch roll encoder in the first scan cycle; s t2 : The speed measurement value of the roller conveyor detected by the pinch roller encoder in the second scanning cycle; s t3 : The speed measurement value of the roller conveyor detected in the third scan cycle of the pinch roller encoder; s tn : The speed measurement value of the roller conveyor detected by the pinch roll encoder in the nth scan cycle; S tn The cumulative value across all scan cycles, i.e., the tail tracking value; Since the physical distance from the rolling center point of the last stand of the finishing mill to the guide plate at the entrance of the coiler is fixed, this physical distance is S. x When the formula judges: S tn ≥S x When the strip tail is about to lose tension control from the pinch rolls and the winding speed needs to be reduced, torque control ends and speed control switches to the winding tail.

2. The multi-stage torque control method for hot-rolled strip tail winding as described in claim 1, wherein in step 1), the strip thickness coefficient K... θ The range of values ​​for is as follows: When the strip thickness is less than or equal to 2.1 mm, K θ =0.982; When the strip thickness is less than or equal to 3.5 mm and greater than 2.1 mm, K θ =0.996; When the strip thickness is less than or equal to 7.5mm and greater than 3.5mm, K θ =1.

052.

3. The multi-stage torque control method for hot-rolled strip tail winding as described in claim 1, wherein in step 1), the strip side pressure coefficient K... S The range of values ​​for is as follows: When the lateral pressure is less than or equal to 70 mm, K S =0.975; when the lateral pressure is less than or equal to 110 mm and greater than 70 mm, K S =0.991; When the lateral pressure is greater than 110mm, K S =1.

034.

4. The multi-stage torque control method for hot-rolled strip coiling as described in claim 1, wherein in step 1), the strip temperature coefficient K... T The range of values ​​for is as follows: When the temperature is less than or equal to 750℃, K T =1.055; K is calculated when the temperature is less than or equal to 950℃ and greater than 750mm℃. T =0.986; when the temperature is greater than 950℃, K T =0.

964.

5. In the multi-segment torque control method for hot-rolled strip tail winding as described in claim 1, in step 2), the value range of the superimposed speed α is 0.2 to 0.8.

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